Device for measuring gas permeation

ABSTRACT

A system for measuring gas permeability of membranes under precise temperature and humidity controls, by the use of a gas detector made from a single metallic block, wherein the gas flow passages are virtually entirely confined within the metallic block, and a temperature control passage is provided in the block for stabilizing temperature of the block and the passages therein, at any predetermined temperature. The detector device also includes passages for forming into liquid reservoirs, for providing a controllable relative humidity by passing the test gases through the mubidifier passages.

This is a continuation of application Ser. No. 07/630,161, filed Dec.19, 1990, now U.S. Pat. No. 5,107,696, issued Apr. 28, 1992.

BACKGROUND OF THE INVENTION

The present invention relates to a device for measuring gas permeabilitythrough a membrane; more particularly, the invention is an improved gaspermeability measuring device which permits such measurements to beaccomplished at substantially constant temperature and relativehumidity.

Gas permeability measuring devices are generally known in the prior art,including a number of such devices which are manufactured by theassignee of the present invention. Such devices typically include one ormore sensing heads which are adapted for holding a membrane materialacross a chamber, wherein a gas such as oxygen may be admitted into thechamber on one side of the membrane, and a detector such as an oxygendetector may be coupled via passages to the other side of the chamber,to measure the amount of oxygen which passes through the membrane. Sinceall membranes are permeable to some extent, it is usually possible todetect a measurable amount of oxygen passing through the membrane over afinite period of time. In the prior art, gas permeability measuringdevices utilized one or more of such measuring heads coupled via hosesand tubing to sensors and the like, to perform fairly accuratemeasurements of membrane permeability.

Measurement of gas permeability through membranes requires extremelysensitive gas detectors or sensors, for the quantities of measured gasare frequently quite low. It is therefore extremely important that theentire system involved in such measurements be maintained under tightlysealed conditions, particularly with respect to all of the gas flowpassages leading to the gas detector. Prior art permeability measuringinstruments typically utilize hoses or tubing to interconnect thenecessary instrumentation, wherein each of the connecting junctions issusceptible to leakage. Since the performance of these instruments canbe critically degraded by gas leakage, it is important to the design ofsuch instruments to provide a minimum number of connections in the gasflow path.

It is also known in the prior art to construct gas permeability sensorsoperating under various conditions of relative humidity of the gas.Relative humidity becomes an important factor in measuring gaspermeability through membranes, because the permeability of certainmembranes is affected by the relative humidity of the membrane and thesurrounding gas. Measuring gas permeability under conditions of highrelative humidity is exceedingly difficult to accomplish, becauserelative humidity and temperature are closely interrelated, and ittherefore becomes necessary to maintain precise control over temperatureif permeability is to be measured under relatively high humidityconditions. Under these conditions it is necessary to controltemperature of all of the gas flow paths in the system, for a 1° C.change in temperature can easily result in a 5% change in relativehumidity. Furthermore, under high relative humidity conditions a slightdecrease in temperature can cause immediate condensation of the gas,resulting in liquid accumulation in the gas flow passages. Therefore itbecomes extremely important to control the temperature of the entiremeasurement system whenever permeability measurements are desired withrespect to humid gases.

Among the systems devised in the prior art for measuring permeabilityare a line of products manufactured by the assignee of the presentinvention under the general model designation "OX-TRAN." These systemshave proved very effective for measuring gas permeability under widelyvarying conditions, although permeability measurement under highhumidity conditions have necessitated relatively expensive and compleximprovements to the basic system models. Examples of patented prior arttechnology can be found in U.S. Pat. No. 3,590,634 "Instrument forDetermining Permeation Rates Through a Membrane," which describes asimple permeation measuring device utilizing dry gases. U.S. Pat. No.4,464,927 "Apparatus for Measuring Gas Transmission Through Films," Aug.14, 1984, describes another simple measuring device utilizing multiplepermeation cells. U.S. Pat. No. 4,852,389 "System for ControlledHumidity Tests," Aug. 1, 1989, discloses a gas permeability measuringdevice capable of operating under different conditions of relativehumidity in the gas. This last patent illustrates the complexity ofequipment which has been necessary in order to accurately accomplishpermeability measurements under conditions of controlled humidity andtemperature.

SUMMARY OF THE INVENTION

The present invention comprises a gas permeability measuring devicewherein humidity and temperature may be precisely controlled, by theexpedient and novel construction of incorporating all of the gaseouspassages into a single metallic block, and by including in the singlemetallic block a temperature control mechanism, wherein the metallicblock possesses exceedingly good heat transfer characteristics so as tobecome a precisely controlled heat sink for the entire system. All ofthe significant gaseous passages in the system are confined to flowpaths through the heat sink, and therefore a uniform and constanttemperature is assured during the measurement process. Water chambersfor introducing humidity into the gases are also confined within theheat sink block so as to ensure that humidity is introduced at the sametemperature as exists throughout the system. A pair of removable cellcovers are clamped against the heat sink, and the necessary flow controland metering valves are all incorporated into the same single metallicblock.

It is the principal object of the present invention to provide a gaspermeability measurement device having improved temperature controlcharacteristics over the prior art.

It is another object of the present invention to provide a gaspermeability measuring device capable of introducing relative humidityinto the measurement gas under precise temperature control conditions.

It is another object of the present invention to provide a gaspermeability measuring device with a minimum number of connections andfittings in the gas flow paths, to reduce the potential for leakage inthe system.

It is a further object of the present invention to provide a gaspermeability measuring device having small and compact size forexpedient operation.

The foregoing and other objects and advantages of the present inventionwill become apparent from the following specification and claims, andwith reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an isometric view of the invention;

FIG. 2 shows a top view of the invention;

FIG. 3 shows a side elevation view of the invention with the removablecover clamp in two positions;

FIG. 4 shows a flow diagram of the invention;

FIG. 5 shows a phantom isometric view illustrating certain gas passagesthrough the invention;

FIG. 6 shows a further phantom isometric view showing further gaspassages through the invention;

FIG. 7 shows an exploded partial phantom isometric view of a portion ofFIG. 6;

FIG. 8 shows a partial cross section of a cell cover;

FIG. 9 shows a cross-section view of a needle valve used in theinvention; and

FIG. 10 shows a cross-section view of a solenoid valve used in theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 1, there is shown an isometric view of gaspermeability detector 10. Permeability detector 10 is adapted forconnection to a source of test gas and a source of carrier gas, which inthe preferred embodiment are sources of oxygen and nitrogenrespectively, and includes two cells for measuring permeability throughtwo different membrane materials. For convenience herein the cells shallbe referred to as "test cell A" and "test cell B." Test cell A comprisesa chamber which may be subdivided into two halves by means of a testmembrane, the chamber being covered by a removable chamber A cover 12.Cover 12 is held securely against the body of permeability detector 10by means of a lock screw 18. Lock screw 18 is threadably secured into alocking clamp 16, and is threadable through locking clamp 16 to engageagainst the outer surface of chamber A cover 12. A similar chamber cover14 exists for chamber B, as does a similar lock screw 20. Locking clamp16 includes two locking clamp arms rigidly interconnected by a hinge rod17. Hinge rod 17 is pivotally held within a hinge rod seat 19. Lockingclamp 16 may therefore be pivotally swung about the axis of rod 17.

Gas detector 10 has a number of adjustable flow valves associatedtherewith; flow valve 102 adjustably controls the flow rate of the testgas oxygen through the device, flow valves 104, 105 and 106 adjustablycontrol the flow of the carrier gas nitrogen through various passages inthe device. All of the flow valves 104, 105, 106 and 102 are needlevalves of a type which will be hereinafter disclosed. In addition to theflow valves described above, the gas detector has a number ofsolenoid-operated on/off valves, such as valve 103 shown on FIG. 1.Valve 103 may be energized by electrical signals via wires (not shown)to open and close certain flow paths in gas detector 10.Solenoid-operated valves of the type used herein will be described inmore detail hereinafter.

The gas detector utilizes a humidifier chamber for each of two gaseswhich may be used with the device; each of the humidifier chambers maybe filled with water or other liquid, and the level of such liquid maybe monitored via sight glasses sealably installed in the detector. Forexample, sight glass 22 opens into the humidifier chamber for thenitrogen component, and sight glass 24 opens into the humidifier chamberfor the oxygen component.

Gas detector 10 has a inlet port 100 for connection to a source ofoxygen, and an inlet port 126 for connection to a source of nitrogen(see FIG. 2). Oxygen is exhausted from an exhaust port 124.

FIG. 3 shows a side elevational view of gas detector 10, showing lockingclamp 16 in solid line in its operable position, clamped against cover12; and also showing locking clamp 16 in dotted outline in its openposition, removed from contact with cover 12. Cover 12 is shown inpartial breakaway, to illustrate one of the gas inlet ports into thechamber formed beneath cover 12.

FIG. 4 shows a system flow diagram of the invention, to illustrate thegas flow and operation of the various components. The oxygen inlet 100is coupled to an oxygen inlet valve 101 which is shown in its normallyopen position in FIG. 4. The oxygen inlet valve 101 is coupled to ahumidifier reservoir 207, and then to the oxygen flow valve 102. Flowvalve 102 permits continuous adjustment of the oxygen flow rate throughthe system. From the oxygen flow valve 102, the oxygen flow paths splitto each of the test cells A and B, wherein each test cell has an oxygeninlet port 213, 214, and an oxygen outlet port 221, 222. After theoxygen outlet ports, the two paths are recombined and are coupled to anoutlet 124.

The nitrogen flow paths shown in FIG. 4 initiate at nitrogen inlet 126.The nitrogen flow path then proceeds to a catalyst chamber 328, and fromthere to a humidifier reservoir 332. A nitrogen purge valve 103 is shownin its normally closed position in FIG. 4. The nitrogen flow path fromreservoir 332 proceeds through three nitrogen flow control valves. Apurge flow control valve 105 is continually adjustable to permitnitrogen to flow through the system to three-way valve 109, where thenitrogen flow may be selectively diverted either to an exhaust outletline 365 or to an outlet port 351. Outlet port 351 is preferablyexternally connected to an oxygen sensor or the like, wherein anaccurate measurement may be made of oxygen content of the gases passingtherethrough. Oxygen sensors of the type described in U.S. Pat. No.3,223,597, Hersch, may be used with the present invention. Nitrogen flowcontrol valves 104 and 106 are also connected to humidifier reservoir332, to permit continuous flow adjustment of nitrogen into each of thetest cells A and B. In each case, nitrogen flows into a test cell inletport 339, 340, through the cell and out an exit port 344, 345. For testcell B, the nitrogen outlet is coupled to a three-way flow valve 308,wherein the nitrogen flow may be selectively valved to an exhaust line359, or to the sensor outlet port 351. Similarly, the nitrogen flowoutlet from test cell A is coupled via passages to three-way valve 307,where it may be selectively switched to an exhaust line 357 or to sensoroutlet port 351.

Referring to FIG. 5, the oxygen passages within gas detector 10 areshown in phantom isometric view. Oxygen inlet port 100 is connected atone end of a passage 201 which is drilled to a predetermined depth intodetector 10. A passage 202 is cross drilled to intersect passage 201,passage 202 forming one opening into oxygen inlet valve 101. Passage 203forms the second opening to oxygen inlet valve 101, and a passage 204 iscross drilled to intersect passage 203, and is drilled to a depthsufficient to intersect humidifier passage 207. Passage 204 is pluggedat the point where it emerges from the surface of detector body 10.Passage 203 is drilled entirely across the thickness of detector 10, andis denoted as passage 205 to the reverse side of detector 10. Passage205 forms one inlet to purge valve 103 which will be describedhereinafter.

Humidifier passage 207 forms a humidifier reservoir, which may be filledor partially filled with water or other liquid, via a fill port 108.Sight glass 24 (see FIG. 1) permits the operator to view the water levelwithin humidifier passage 207. Oxygen flow valve 102 is threadablysecured into passage opening 210, and passage 210 is extended downwardlyto intersect humidifier passage 207 via passage 209. A passage 212 iscross drilled to intersect passage 210, passage 212 forming an exit port213 at one surface of detector 10, and an exit port 214 at the othersurface of detector 10. Exit ports 213 and 214 are oxygen inlet ports tothe respective chambers A and B, with exit port 213 forming a part ofchamber A and port 214 forming a part of chamber B. The respective gasflow exit ports from chambers A and B are ports 221 and 222, which areformed at the ends of a cross-drilled passage 223. A passage 224 iscross drilled to intersect passage 223, and passage 224 is connected tooxygen exhaust port 124 at the surface of detector 10. The foregoingpassages represent the oxygen flow passages through gas permeabilitydetector 10.

An enlarged passage 250 opens through an end surface of detector 10, andextends to a depth of approximately two-thirds of the length of detector10. Passage 250 may be used to insert a temperature control device intothe interior of detector 10, for the purpose of stabilizing thetemperature of detector 10 at any predetermined temperature. Forexample, an electrical heating element may be inserted into passage 250for the purpose of elevating the temperature to a predeterminedtemperature above ambient. As a further example, a flow of liquid at anypredetermined temperature may be circulated through passage 250, forpurposes of either heating or cooling. Because the entire detector 10 ismade from a single metallic block, it is relatively easy to stabilizethe temperature of the entire block, and therefore all of the internalpassageways, through the use of heating and/or cooling media in passage250.

FIGS. 6 and 7 show the nitrogen flow passages in gas detector 10, inphantom isometric view. A nitrogen inlet port 126 is connected to apassage 327, which is cross drilled into a larger passage 328. Thelarger passage may have a catalyst material inserted therein, andpassage 328 is enclosed by means of a removable plug 326. The catalystmaterial may be a type which will remove contaminants from the carriergas flow. Passage 328 has a lower extended passage 331 which intersectsand opens into humidifier passage 332. Humidifier passage 332 forms ahumidifier reservoir, which may be filled or partially filled with wateror other liquid via a fill port 133. A sight glass 22 (see FIG. 1)permits the operator to view the liquid level within humidifier passage332.

A small passage 330 is cross drilled into passage 328, and passage 330opens to the rear surface of detector 10. A two-way purge valve 103 isaffixed to the outer surface of detector 10 at the opening of passage330, to provide a controllable flow path between passage 330 and passage205. Passage 205 opens into the oxygen passages described hereinbefore.A passage 335 is drilled to open into humidifier passage 332, passage335 also opening into an enlarged opening for placement of a purge flowvalve 105. A second passage 361 is cross drilled into the enlargedopening adjacent passage 335, and the flow path between the passages 361and 335 is controlled by purge flow valve 105. A passage 362 is crossdrilled to intersect with passage 361, passage 362 being brought to thelower surface of detector 10, closely adjacent to parallel passage 364.A three-way purge selection valve 109 is affixed at the exterior openingof passages 362 and 364, to regulate the flow therebetween. Passage 364is cross drilled to open into passage 350, which opens through the sidesurface of detector 10 at port 351. A suitable connector may bethreadably secured to port 351, to connect to an external oxygen sensor.

A further passage 349 is cross drilled to open into passage 350, and isopened through the lower surface of detector 10, closely adjacent aparallel passage 347. A three-way valve 308 is affixed to the lowersurface of detector 10, to regulate the flow path between passages 347and 349. Passage 347 is cross drilled to open into a passage 345, andpassage 345 opens into the B cell on the side of detector 10. A passage348 also opens into passage 350, and is opened to the lower surface ofdetector 10, closely spaced with passage 346. A three-way valve 107 isaffixed to the lower surface to regulate the flow between passages 346and 348. Passage 346 also opens into a passage 344, which itself opensinto the A cell chamber. A second passage opening into the A cellchamber is passage 339, which is also drilled to intersect with anenlarged passage 338. Passage 338 is drilled sufficiently deep to openinto humidifier passage 332, and the top opening of passage 338 is sizedto accommodate a nitrogen flow valve 106. A further passage 341 is crossdrilled to intersect passage 339, and opens through the top surface ofdetector 10. A removable plug is sealably inserted into passage 341 forpurposes to be hereinafter described.

A further passage 334 is cross drilled downwardly to open intohumidifier passage 332, and a passage 337 is cross drilled from the sidesurface into passage 334. Passage 337 opens into the cell B chamber. Theenlarged top opening of passage 334 is sized to accept a nitrogen flowvalve 104, to regulate the flow rate of nitrogen into cell B. Finally, apassage 333 is cross drilled to open into humidifier passage 332,passage 333 having a removable top plug to permit the filling of fillpart 133 with water or other liquid.

Referring to FIG. 7, some of the nitrogen flow passages are shown inexploded view. Passage 362 is cross drilled from below to open intopassage 361, and passage 361 opens into passage 335. Passage 335 has alower opening into humidifier passage 332, and has an upper openingthrough the top surface of detector 10 which is sized to accommodate thepurge flow valve 105. Passage 205 and 330 are brought out through theside surface of detector 10, and the flow between these passages isregulated by a two-way nitrogen purge valve 103.

FIG. 8 shows a side cross-section view of the elements which form thetest chamber. For ease of illustration, the inlet and outlet ports intothe chamber have been rotated in this cross-section view so as to appearalong a common plane; it is understood that in the actual unit the inletand outlet ports may be positioned along different intersecting planesof the chamber. A clamping force indicated by arrow 120 is appliedagainst cover 12, by the combined effect of locking clamp 16 and lockscrew 18. This clamping force securely holds cover 12 against the bodyof detector 10, and clamps an intermediate test membrane 122 betweencover 120 and the body of detector 10. Membrane 122 may be formed of athin plastic film or other similar material, to form a barrier between acover chamber 402 and a body chamber 404. An O-ring 400 is seated aboutthe periphery of the chambers formed thereby, so as to provide a sealedenclosure.

An oxygen inlet port 213 is formed by a hollow pin 406 which is affixedin cover 12. Hollow pin 406 is insertable into a corresponding openingin the body of detector 10, and an O-ring 407 assures a tight gas seal.A passage 408 is cross drilled in cover 12 to intersect inlet passage213, and a second passage 410 is cross drilled to intersect passage 408.Passage 408 opens into chamber 402 to permit the flow of oxygen intochamber 402. An oxygen outlet 221 is formed by a similar hollow pin 416affixed to cover 12, and a passage 418 is cross drilled to intersectpassage 221. A small passage 420 is cross drilled to intersect passage418, and thereby to provide an opening into chamber 402. Oxygen flowsthrough the chamber 402 and out the outlet port 221, whereby hollow pin416 is sealably coupled to the body of detector 10 by means of an O-ring417.

A nitrogen inlet passage 339 opens into chamber 404, and a nitrogenoutlet passage 344 also opens into chamber 404. Nitrogen is thereforepermitted to flow into chamber 404 via inlet 339 and out of chamber 404via outlet 344. The outer ends of passages 408 and 418 are plugged asillustrated in FIG. 8. A port 430 is shown in dotted outline in FIG. 8,which port may be closed by a removable plug. The purpose of port 430 isto permit the insertion of a relative humidity probe into the oxygenchamber 402, so that external measurements may be made to determine therelative humidity within chamber 402.

FIG. 9 shows a cross-sectional view of a typical flow valve, for exampleflow valve 102. Flow valves 102, 104, 105 and 106 are all made accordingto the illustration of FIG. 9, and are commercially available flowvalves. One commercially available valve which may be used in connectionwith this invention is a valve designated as a flow control valve No.5947L001GEA, manufactured by Brooks Instrument Division, EmersonElectric Company, Hatfield, Pa. Flow valve 102 has an inlet port 209which is sealably blocked by a portion of the valve body 501, incooperation with O-ring 502. A retractable valve body portion 503 isconnected to valve knob 504. Valve knob 504, and retractable portion503, may be threadably inserted into or retracted out of the valve,thereby inserting and/or withdrawing a tapered needle 506 into a port507. As the needle is threadably retracted from the port 507 anincreasing gap appears between the needle and the port, therebyproviding a flow communication path from inlet 209 to outlet 211. Theflow rate passing through the valve may thereby be controlled byselective adjustment of the valve.

FIG. 10 shows an illustration of a typical two-way or three-way solenoidvalve as used with the present invention. These valves are alsocommercially available, from Precision Dynamics, Inc., of New Britain,Conn. The two-way solenoid valve is available under Type DesignationG-2014-MM-512, and the three-way solenoid valve is available under TypeDesignation G-3114-MM-S7. In both cases, the overall valve constructionis very similar. For example, referring to FIG. 10, an upper plug 520 isshown in dotted outline, threadably secured to block a passage throughthe top of the valve. In the case of a two-way solenoid valve, plug 520is inserted as shown in FIG. 10; in the case of three-way valve, plug520 is omitted from the construction. Referring to purge selection valve109 by way of example, there is an annular inlet port 363 which maycommunicate with either an outlet port 364 or an outlet port 365. Whenthe solenoid is energized, the slidable valve section 521 moves upwardlyto block opening 522, and to unblock opening 523. In this position,inlet port 363 is in flow communication with outlet port 364. If thesolenoid valve is deenergized slidable element 521 moves downwardly toblock inlet opening 523 into open inlet 522. This permits flowcommunication between inlet port 363 and outlet port 365.

In the present invention, oxygen inlet valve 101 and purge valve 103 areeach two-way solenoid valves; purge selection valve 109, and nitrogenselection valves 307 and 308 are each three-way solenoid valves.

In operation, a film membrane which is to undergo tests is mounted intoeach of the chambers A and B, by inserting a section of the filmmembrane between a cover and the body of detector 10. The respectivelock screws are tightened to fully compress the cover and film membraneagainst the body of detector 10, thereby to assure a leak-freeconnection. The oxygen inlet valve is shut off, all of the solenoidvalves are deenergized, and the nitrogen purge valve is turned on,thereby to permit nitrogen to flow through the passages of the system topurge undesirable gases from the system. At the same time, the flowcontrol valves may be adjusted to accommodate the desired flow rate ofgases through the system during a test procedure. If desired, a suitabletemperature medium is introduced into the temperature control passage250, until the system temperature has stabilized at some preselectedtemperature value.

When a desired test procedure is undertaken, the nitrogen purge valve isfirst shut off and the oxygen inlet valve is turned on, to permit theflow of oxygen into the two test cells on one side of each of the filmmembrane barriers. A flow of nitrogen may be maintained through the testcells on the other side of the film membranes, and one or more of theselection valves may be activated to permit gas flow from either of thetest cells to pass to a gas sensor device connected to outlet port 351.The measurements made by the gas sensor device are recorded andmaintained over predetermined time, thereby to provide a measure ofoxygen permeability of the respective test membranes under thepredetermined test conditions.

The test procedure may be performed under controlled relative humidityconditions by use of the respective humidity reservoirs, and a nitrogenrelative humidity measurement may be made via a relative humidity sensorconnected at an inlet port coupling 341. An oxygen relative humiditymeasurement may be made via a relative humidity sensor connected atinlet port 430. Relative humidity calculations may be made by thetwo-pressure method. The inlet pressures of both the test gas and thecarrier gas is controlled by a pressure regulator (not shown), at somepressure elevated above atmospheric pressure. Therefore, the elevatedpressure in humidifiers 207 and 332 exceeds atmospheric pressure, andthe relative humidity in each of these humidifiers is 100% RH. Therelative humidity at any point subsequent to the humidifiers is directlyproportional to the pressure drop at that point. For example, if a gasis at 100% RH at a pressure of 30 psia, and the gas is exhausted toambient pressure (15 psia), the relative humidity of the exhaust gas is50% RH.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof, and it istherefore desired that the present embodiment be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims rather than to the foregoing description to indicatethe scope of the invention.

What is claimed is:
 1. Apparatus for measuring gas permeability of amembrane material, comprising:a. a material volume formed of a solidmetal block having high thermal conductivity characteristics so as tomaintain a substantially uniform temperature throughout all regions ofits volume; b. at least one first cavity formed on an exterior surfaceof said material volume, said at least one first cavity being surroundedby a peripheral flat surface formed on said exterior surface; c. atleast one removable cover sealably affixable against said peripheralflat surface, said at least one cover having a second cavity which isalignable with said at least one first cavity, including means forclamping said membrane material between said cavities; d. a plurality ofpassages formed in said material volume and said removable cover,includingi) a first set of passages in the interior of said materialvolume, having a first opening through a surface of said materialvolume, and a second opening into one of said first cavities, and meansfor connecting said first opening to a first source of gas; ii) a secondset of passages in the interior of said material volume, having a firstopening through a surface of said material volume, and a second openinginto said second cavity, and means for connecting said first opening toa second source of gas; iii) a third set of passages in the interior ofsaid material volume, having a first opening into one of said firstcavities, and a second opening through a surface of said materialvolume; iv) a fourth set of passages in the interior of said materialvolume, having a first opening into said second cavity, and a secondopening through a surface of said material volume; e. means forconnecting a gas detector to one of said second openings of said thirdset of passages or said fourth set of passages; f. a fifth set ofpassages in the interior of said material volume, said fifth set ofpassages having a first and second opening through a surface of saidmaterial volume; and g. means for connecting the first and secondopenings of said fifth set of passages to a source of heat transferliquid whereby the heat transfer liquid passing through said fifth setof passages determines the temperature of the entire material volume andpassages therein.
 2. The apparatus of claim 1, further comprising afirst valve attached to said material volume, said first valve having agas flow regulating member extending into said first set of passages,thereby to control the gas flow rate therethrough.
 3. The apparatus ofclaim 2, further comprising an enlarged passage section entirely withinthe interior of said material volume, comprising a portion of said firstset of passages, said enlarged section formed into a liquid reservoir;and a liquid fill passage extending from said enlarged section to thesurface of said material volume.
 4. The apparatus of claim 3, furthercomprising a second valve attached to said material volume; andbranching passages between said first set of passages and said secondset of passages; said second valve having a passage closure memberextending into said branching passages, thereby to open and close saidbranching passages.
 5. The apparatus of claim 4, further comprisingmeans for measuring the relative humidity in at least one of saidcavities.
 6. The apparatus of claim 5, wherein said material volumefurther comprises a unitary structure made from a metal.
 7. Theapparatus of claim 6, wherein said metal further comprises aluminum. 8.The apparatus of claim 7, wherein said first source of gas furthercomprises a source of oxygen.
 9. The apparatus of claim 8, wherein saidsecond source of gas further comprises a source of nitrogen.
 10. Anapparatus for measuring gas permeability of a membrane material undercontrolled humidity conditions, comprising:a. a material volume formedof a solid metal block having good thermal conductivity characteristicsso as to maintain a substantially uniform temperature throughout allregions of said volume; b. a plurality of gas-conveying passages in theinterior of said material volume, including at least one enlargedchamber formed wholly within the interior of said material volume in atleast one of said passages, and a fill passage extending from said atleast one enlarged chamber to the surface of said material volume; andc. a plurality of further passages in the interior of said materialvolume, said further passages coupled to a first and second openingthrough the surface of said material volume, and means for connecting asource of heat transfer liquid to said first and second openings, andmeans for circulating said heat transfer liquid through said furtherpassages, whereby to control the temperature of said material volume.11. The apparatus of claim 10, further comprising a first enlargedrecess in the exterior surface of said material volume, at least two ofsaid plurality of gas-conveying passages opening into said firstenlarged recess; a further material volume having a further enlargedrecess in one surface thereof; means for aligning said further enlargedrecess with said first enlarged recess and means for clamping saidfurther material volume against said material volume with saidrespective enlarged recesses in alignment; and means for connecting atleast two further of said plurality of gas-conveying passages into saidfurther enlarged recess.